35 lines
1.5 KiB
Markdown
35 lines
1.5 KiB
Markdown
# Systems >> Form >> ModelValue ||20
|
||
|
||
The modelValue or model can be considered as the ‘aorta’ of our form system.
|
||
It is the single source of truth; not only for the current state
|
||
of the form, also for all derived states: interaction, validation, visibility and other states are
|
||
computed from a modelValue change.
|
||
|
||
## Single source of truth
|
||
|
||
ModelValues are designed to provide the Application Developer a single way of programmatical
|
||
interaction with the form for an Application Developer.
|
||
|
||
### One single concept for Application Developers
|
||
|
||
Application Developers need to only care about interacting with the modelValue on a form control
|
||
level, via:
|
||
|
||
- `.modelValue`
|
||
- `@model-value-changed`
|
||
|
||
> Internal/private concepts like viewValue, formattedValue, serializedValue are therefore not
|
||
> recommended as a means of interaction.
|
||
|
||
For more information about parsing and the Unparseable type, see [Formatting and Parsing](../../../docs/systems/form/formatting-and-parsing.md)
|
||
|
||
### Event meta
|
||
|
||
`model-value-changed` events have a `detail` object, containing the following meta data:
|
||
|
||
- `isTriggeredByUser`: a boolean that determines whether a change originated
|
||
from a user or was triggered programmatically
|
||
- `formPath`: an array of FormControls. It contains the path an event follows to go from a 'leaf
|
||
element' (for instance a lion-input) to a top element (for instance lion-form). An example path
|
||
could be [lionForm, lionFieldset, lionInput]
|
||
- `initialize`: whether this is the first time the event is fired (on first render of the FormControl)
|